There are many types of data storage, each having their own advantages. For example, known data storage includes Solid State Drives (SSD), Hard Disk Drives (HDD), as well as newer technologies such as Phase Change Memory and Racetrack technology based disk storage. These technologies have different data remanence rules, each of which may require different levels of overwrites in order to sanitize the data.
SSD is based on volatile memory such as DRAM and is characterized by ultrafast data access, generally less than 10 microseconds. SSD is known to have fast start-up because there are no spin-up requirements. Also, SSD has fast random access because there is no read/write head. SSD is also known to have low read latency times and consistent read performance due to the location of data being irrelevant for SSD. For these and other reasons, SSD is becoming more common in the market place (as the advantages of SSD over disk drive storage are becoming more apparent).
HDD, on the other hand, is a non-volatile storage device that stores digitally encoded data on rapidly rotating disks with magnetic surfaces. HDD, unlike SSD, requires read/write heads as well as requiring spin-up. The spin-up requirement, though, is known to slow start up.
Phase-change memory (also known as PCM, PRAM or PCRAM) is a type of non-volatile computer memory. PRAM is one of a number of new memory technologies that are competing in the non-volatile role with Flash memory. PRAM uses the unique behavior of chalcogenide glass, which can be “switched” between two states with the application of heat, i.e., crystalline and amorphous. Recent versions of PRAM achieve two additional distinct states effectively doubling its storage capacity. Racetrack Memory is an experimental non-volatile memory device currently under development by International Business Machines Corp. It is expected that Racetrack will offer storage density higher than comparable solid-state memory devices like Flash RAM and similar to conventional disk drives, but with much higher read/write performance.
The level of overwrites required for each of these technologies may vary, depending on the level of security. For example, the level of overwrites required for a file present on HDD will be far more than a file present on SSD for secure file deletion. This is purely because both are different technologies of storing the underlying data. For this reason, there will be different data remanence rules for data residing on SSD and HDD, as well as other technologies. Of course, this creates an optimization problem for data remanence as some technologies may require a different number of overwrites than other technologies.
Data remanence is the residual physical representation of data that has been erased or overwritten. Minimizing data remanence is an act of securely purging the content such that there are no remains on storage. Specific methods of data remanence include overwriting, purging, degaussing, encryption, and physical destruction depending on the level of security and type of data storage. Specifically, a common method used is to overwrite the storage medium with new data. This is often called wiping or shredding a file or disk. Overwriting is generally an acceptable method of clearing, as long as the media is writable and not damaged. This methodology is a popular, low-cost option for some applications.
Data remanence is one of the vital aspects for data security over storage, as mandated by regulatory compliances. In fact, various standards of data remanence are published by the Department of Defense (DoD). For example, secure purging of data at file level to meet data remanence is the most common approach. Some of the delete operations over a file system can be extended to support different specifications of data remanence to implement secure delete. However, since data remanence involves multiple level of writing with different formats (depending upon the specification being implemented) it proves to be a costly to system performance as it is performing multiple I/O operations.
A problem is the data sanitization secure deletion of data is a costly affair as it involves multiple write cycles over file contents, before the file is deleted. Setting the incorrect overwrite level for each storage device optimizes the performance by reducing the deletes, rewrite, and reads on the disk. It also ensures the proper security level is applied to each disk across a sanitized delete. For example a file with size 1 GB may be striped across hybrid storage such that 250 MB of file data resides on HDD while 750 MB resides on SSD. Assuming that five (5) levels of overwrites on HDD is equivalent to three (3) levels of overwrite on SSD for same level of data sanitization, the existing methods execute 5 levels of overwrite across the entire 1 GB file without considering the underlying disk technology. So 750 MB of data which actually required only 3 levels of overwrite end up having 5 levels of overwrite impacting cost and performance. These processes are more performance intensive which consumes more power and is less environmentally friendly.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described herein above.